text: In the solid state of their salts, metaborate ions are often oligomeric or polymeric, conceptually resulting from the fusion of two or more  through shared oxygen atoms. In these anions, the boron atom forms covalent bonds with either three or four oxygen atoms. Some of the structures are:
  * A trimer with formula  or , consisting of a six-membered ring of alternating boron and oxygen atoms with one extra oxygen atom attached to each boron atom. This form is found, for example, in some anhydrous alkali metal salts like sodium metaborate or potassium metaborate, in α- and β-barium metaborate , and in the mixed salt potassium cadmium metaborate . The three B–O distances are nearly equal in the potassium salt (133.1, 139.8, and 139.8 pm) but significantly different in the sodium one (128.0, 143.3, and 143.3 pm).
  * A polymer of  units connected by single shared-oxygen bridges; that is, . Occurs in calcium metaborate  or .
  * A tridimensional network of  tetrahedral groups, as in "zinc metaborate", which is actually a mixed salt zinc metaborate oxide, with the formula .
  * A tridimensional regular array of  tetrahedra sharing oxygen vertices, as in the high-pressure and high-temperature γ form of lithium metaborate .